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A077091 When iteration of f[]=Phi[](Sigma[]-Phi[]) is started at composite initial values listed here it ends at a nonzero fixed point. 2
1, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 38, 39, 42, 44, 45, 46, 49, 51, 54, 55, 56, 57, 58, 62, 63, 65, 68, 69, 70, 74, 75, 77, 82, 85, 86, 87, 91, 93, 94, 95, 99, 104, 111, 115, 119, 121, 125, 129, 133, 134, 143, 145, 153 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
EXAMPLE
n=30: FixedPointList={30,32,46,20,16,22,12,8,10,6,4},end=4; n=94:FixedPointList={94,42,24},end=24.
MATHEMATICA
f[x_] := EulerPhi[DivisorSigma[1, x]-EulerPhi[x]] Do[s=NestList[f, n, 100]; s1=Part[s, 99]; s2=Part[s, 100]; If[Equal[s1, s2]&&!PrimeQ[n], Print[{n, s1}]], {n, 1, 1000}]
CROSSREFS
Sequence in context: A141468 A140347 A140209 * A340268 A340058 A174891
KEYWORD
nonn
AUTHOR
Labos Elemer, Oct 31 2002
STATUS
approved

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Last modified June 20 22:01 EDT 2024. Contains 373532 sequences. (Running on oeis4.)